Search found 30 matches
- Sat Mar 16, 2019 12:50 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Galvanic cells and K
- Replies: 3
- Views: 331
Re: Galvanic cells and K
I would use the equation of E=R*T/(nF)*lnK. Isolate K to solve, assuming you have values for the other variables or the information needed to solve them.
- Tue Mar 12, 2019 4:39 pm
- Forum: Ideal Gases
- Topic: units
- Replies: 15
- Views: 1402
Re: units
The units in K should cancel out so there shouldn't be any units for K.
- Tue Mar 12, 2019 4:30 pm
- Forum: Zero Order Reactions
- Topic: Reaction Rate
- Replies: 10
- Views: 1241
Re: Reaction Rate
Yes as long as it is the same formula and under same conditions (ex. temp)
- Mon Mar 11, 2019 10:12 pm
- Forum: First Order Reactions
- Topic: Units of Rate Constant
- Replies: 5
- Views: 665
Re: Units of Rate Constant
Not necessarily. As long as the units can cancel out, you can do seconds, minutes, hours, etc.
- Mon Mar 11, 2019 10:10 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Final Exam Topics
- Replies: 8
- Views: 838
Re: Final Exam Topics
Yep everything up to and including Wednesday
- Mon Mar 11, 2019 3:44 pm
- Forum: First Order Reactions
- Topic: First order rxn graphs [ENDORSED]
- Replies: 4
- Views: 528
Re: First order rxn graphs [ENDORSED]
They all have time on the x axis
Zero order has [A] on the y axis and slope is -k
First order has ln[A] on the y and slope is also -k
Second order has 1/[A] on the y and slope is k
Zero order has [A] on the y axis and slope is -k
First order has ln[A] on the y and slope is also -k
Second order has 1/[A] on the y and slope is k
- Mon Mar 11, 2019 3:27 pm
- Forum: Reaction Mechanisms, Reaction Profiles
- Topic: Frequency Factor
- Replies: 5
- Views: 557
Re: Frequency Factor
It is the number for the frequency of collisions between reactants.
- Mon Mar 11, 2019 3:19 pm
- Forum: Arrhenius Equation, Activation Energies, Catalysts
- Topic: "Bottle Neck" Pre-equilibrium Approach
- Replies: 1
- Views: 247
Re: "Bottle Neck" Pre-equilibrium Approach
The Pre-equilibrium approach assumes that the reaction has steps in the order of a fast step, then a slow step. The fast step will produce intermediates needed for the slow step and because the slow step is slow, there will be a build up of intermediates and we can assume that it will be at equilibr...
- Sun Feb 24, 2019 6:51 pm
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: Ecell
- Replies: 13
- Views: 1505
Re: Ecell
Ecell can be calculated by subtracting the reduction potential of the half reaction that is oxidized from the reduction potential of the half reaction that is reduced.
- Sun Feb 24, 2019 6:49 pm
- Forum: Balancing Redox Reactions
- Topic: Order to balance
- Replies: 6
- Views: 582
Re: Order to balance
In half reactions, balance elements first, H and O second, electric charges third and then electrons last.
- Sun Feb 24, 2019 6:48 pm
- Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
- Topic: Spontaneous?
- Replies: 6
- Views: 770
Re: Spontaneous?
If the change in Gibbs free energy is negative, then it it spontaneous
- Sun Feb 24, 2019 6:46 pm
- Forum: Student Social/Study Group
- Topic: How are you guys going to study for Test 2?
- Replies: 10
- Views: 1028
Re: How are you guys going to study for Test 2?
Doing hw problems
- Mon Feb 18, 2019 11:17 pm
- Forum: Thermodynamic Systems (Open, Closed, Isolated)
- Topic: TEST 3
- Replies: 7
- Views: 1017
Re: TEST 3
All topics on Gibbs free energy and electrochemistry
- Mon Feb 18, 2019 11:15 pm
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: standard Gibbs Free Energy
- Replies: 4
- Views: 542
Re: standard Gibbs Free Energy
Standard gibbs energy is denoted by the little degree-like symbol and indicates the gibbs energy when the process is under 1 atm and 25 degrees C.
- Mon Feb 18, 2019 11:14 pm
- Forum: Thermodynamic Systems (Open, Closed, Isolated)
- Topic: Internal energy (U) of an isolated system
- Replies: 17
- Views: 2726
Re: Internal energy (U) of an isolated system
In an isolated system, there is no exchange of energy with surroundings and therefore the internal energy stays the same and delta U is 0
- Mon Feb 18, 2019 11:08 pm
- Forum: Calculating Standard Reaction Entropies (e.g. , Using Standard Molar Entropies)
- Topic: Isolated system
- Replies: 10
- Views: 1317
Re: Isolated system
Heat and matter cannot be moved in or out of the bomb calorimeter
- Mon Feb 18, 2019 11:08 pm
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: Negative Delta G
- Replies: 7
- Views: 4158
Re: Negative Delta G
When delta H is negative and delta S is positive, it will definitely be negative delta G.
A large negative delta H and a small negative delta at a low temperature can possibly result in a negative delta G
A large negative delta H and a small negative delta at a low temperature can possibly result in a negative delta G
- Sat Feb 09, 2019 3:57 pm
- Forum: Entropy Changes Due to Changes in Volume and Temperature
- Topic: When to use deltaS=q/t versus deltaS=nRlnV2/V1
- Replies: 2
- Views: 377
Re: When to use deltaS=q/t versus deltaS=nRlnV2/V1
Use deltaS=q/t when q (heat transferred) and temperature is given. Use deltaS=nRlnV2/V1 when moles and volume change is given.
- Sat Feb 09, 2019 3:51 pm
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: When do you use w = -nRTlnV2/v1, q = nRTlnV2/V1, and w = -PdV?
- Replies: 1
- Views: 430
Re: When do you use w = -nRTlnV2/v1, q = nRTlnV2/V1, and w = -PdV?
Use w=nRTlnV2/V1 when solving for work done by a reversible, isothermal gas expansion process with Volume change. Use w=-PdV for irreversible gas work. q is for heat transferred but I think that specific equation is not frequently used.
- Sat Feb 02, 2019 12:23 pm
- Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
- Topic: Delta U
- Replies: 3
- Views: 699
Re: Delta U
Delta U only requires the Final and Initial numbers of U and anything that takes place in between (the path) does not matter. Because delta U just means the change of U from the beginning to the end, it is a state function.
- Sat Feb 02, 2019 12:14 pm
- Forum: Thermodynamic Systems (Open, Closed, Isolated)
- Topic: open system
- Replies: 8
- Views: 1387
Re: open system
When the beaker is open, it experiences a constant pressure since the pressure it experiences is the atmospheric pressure around it which will not change since the atmosphere is too large for any change to be considered significant.
- Sun Jan 27, 2019 9:30 pm
- Forum: Phase Changes & Related Calculations
- Topic: State Properites
- Replies: 7
- Views: 669
Re: State Properites
State properties do not depend on the path taken; they depend on the state of the substance. Work and heat are not considered because they take into account the path taken. Ex. In work, the formula is force times distance. If you have two molecules at the same starting point, molecule A that reaches...
- Sun Jan 27, 2019 9:19 pm
- Forum: Ideal Gases
- Topic: Approximations for ICE
- Replies: 20
- Views: 1664
Re: Approximations for ICE
when the K is less than 1x10-3, so if the K ends with 10^-4 or smaller. Ex 1.9x10^4 approximate but 1.9x10^-3 don't approximate
- Sun Jan 27, 2019 9:15 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Catalysts in Kc
- Replies: 6
- Views: 726
Re: Catalysts in Kc
They increase the rate of the reaction but does not cause any permanent chemical change in the reaction, so the concentrations are the same and equilibrium is the same
- Sun Jan 27, 2019 9:12 pm
- Forum: Phase Changes & Related Calculations
- Topic: Phase Changes
- Replies: 7
- Views: 933
Re: Phase Changes
They are both endothermic because they need to take in heat to break bonds and change phase
- Mon Jan 21, 2019 5:10 pm
- Forum: Calculating the pH of Salt Solutions
- Topic: pH of acids
- Replies: 13
- Views: 3608
Re: pH of acids
Strong acid will have lower pH because it has a full dissociation into more H30+ than a weak acid. pH relies on the amount of H30+ ions (-logH30+) and so more H30+ ions will cause the pH to be lower since you are logging the molarity.
- Mon Jan 21, 2019 5:07 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: 5% rule
- Replies: 12
- Views: 21877
Re: 5% rule
If the % pronotation is less than 5, then approximation (disregarding the initial change of x in the denominator) is valid.
- Thu Jan 10, 2019 4:41 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: 6th edition, 11.7?
- Replies: 4
- Views: 347
Re: 6th edition, 11.7?
Thanks that's really helpful. Just wanted to know why would 5/17 be used for the calculation of partial pressure instead of 6/11 from the earlier part B?
- Thu Jan 10, 2019 4:29 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: H2O
- Replies: 5
- Views: 390
Re: H2O
Yes, water in gas form in included, however water in liquid form is not.
- Thu Jan 10, 2019 4:22 pm
- Forum: Ideal Gases
- Topic: Reaction Quotient
- Replies: 6
- Views: 433
Re: Reaction Quotient
We disregard solids and liquids because their concentrations are the same throughout the reaction. Concentration equals to density divided by molar mass and both solids and liquids' densities are pretty much constant, therefore concentrations of solids and liquids are constant.